The invention relates to a fiber reinforced composite wherein the fiber comprises melt blown fibers and a method therefor.
Fiber reinforcement of elastomeric articles is well known in the art. Conventional fiber reinforcement usually improves the modulus properties of an elastomer while sacrificing tensile properties, tear properties and hysteresis properties. Accordingly, the amount of a fiber reinforcement used in an elastomer is usually a trade off between the increase in modulus desired and the loss of other properties that can be tolerated.
Kevlar.RTM. (polyaromatic amide) fibers are one of the most widely used reinforcing fibers. Such fibers are expensive, although they do provide excellent modulus properties in an elastomeric matrix in which they are used. Conventional Kevlar.RTM. fibers are ordinarily used in low concentration in rubber products (about 2 to 8 phr (parts by weight per hundred parts by weight rubber)) because of their large size and because they do not mix well with rubber, and do not adhere well to rubber. Because of their large size and low adhesion, if the Kevlar.RTM. fibers are used in too high concentration, they tend to weaken the elastomer matrix.
Recently, the trend has been to try using micro fibers as elastomer reinforcement in order to obviate some of the problems described above. Micro fibers are, on average, on the order of 0.1 to 10 microns in diameter, with an aspect ratio of 1 to, substantially, infinity. Micro fibers have been made from many materials, some of which show good adhesion and good compatibility with rubber.
One method of incorporating thermoplastic microfibers in an elastomer is to co-extrude a thermoplastic polymer with an elastomer according to Goodyear Tire & Rubber Co. U.S. Pat. No. 5,364,905 issued Nov. 15, 1994 and U.S. Pat. No. 5,225,457 issued Jul. 6, 1993. Unfortunately, only thermoplastics that have a melting point close to the processing temperature of the elastomer can be used in this technique. There is no method provided in the art for incorporating microfibers of some of the most economical and useful reinforcing fibers, such as PET, nylon 6, polyurethane, high syndiotactic poly (1,2-butadiene) (Syndio), and block copolymer such as polystyrene/olefin/styrene in an elastomer. An example of the latter is Kraton.RTM. polymer, available from Shell Chemical Company.
It is an object of this invention to provide a method for incorporating micro fibers, that have melting points outside the range of the processing temperature of elastomers, into an elastomer. It is also an object of the invention to provide an elastomer reinforced with such fibers. Other objects of the invention will be apparent from the following description and claims.